When activated, a cruise control system implemented in a motor vehicle automatically controls the vehicle's speed. Through a user interface of the cruise control system, the vehicle operator (i.e., the “driver”) may activate the cruise control system, deactivate the cruise control system, and set or adjust a target speed for the vehicle. Once activated, the cruise control system compares the actual speed of the vehicle with the target speed, and controls the operation of the vehicle's speed in order to attempt to maintain the target speed.
For example, when the vehicle's actual speed is less than the target speed, the cruise control system may cause the vehicle to accelerate by providing throttle control signals to increase the throttle input (e.g., causing the throttle to increase air flow to the engine) and/or by providing transmission control signals to cause the vehicle's transmission to downshift. Alternatively, when the vehicle's actual speed is greater than the target speed, the cruise control system may cause the vehicle to decelerate by providing throttle control signals to decrease the throttle input (e.g., causing the throttle to decrease air flow to the engine) and/or by providing transmission control signals to cause the engine to perform engine braking (e.g., causing the transmission to downshift without increasing the throttle input). Once the cruise control system determines that the actual speed has reached the target speed, the cruise control system may operate the speed in a steady state matter in order to maintain the target speed.
Although conventional cruise control systems may be a great convenience to drivers, under some circumstances, conventional cruise control systems may operate in a manner that is inherently inefficient, in terms of fuel economy. For example, when a conventional cruise control system detects a fairly large difference between a vehicle's actual speed and a target speed (e.g., 5 miles/per hour (mph) or more), the cruise control system may cause the vehicle to accelerate aggressively in order to reach the target speed. This aggressive acceleration may be accomplished, for example, by causing the transmission to downshift and by causing a significant increase in the throttle input. A vehicle tends to consume more fuel while aggressively accelerating than while gradually accelerating and, accordingly, aggressive acceleration results in decreased fuel economy.
The inefficiencies in fuel economy due to aggressive acceleration are exacerbated in heavy traffic and other scenarios. For example, each time a vehicle operating with its cruise control system activated approaches slower traffic ahead of the vehicle, the driver must either apply the brake, deactivate the cruise control system or maneuver around the traffic in order to avoid a collision. When the driver repeatedly brakes and/or deactivates and re-activates the cruise control system, the cruise control system may cause the vehicle repeatedly to accelerate aggressively, thus adversely affecting the vehicle's fuel economy. Similar inefficiencies may occur in areas where the speed limits repeatedly change and in areas where the roads include non-gradual turns. In such areas, a driver may be forced repeatedly to brake, to re-set the target speed, and/or to deactivate and re-activate the cruise control system in order to comply with the speed limit restrictions or to maneuver around the turns. In addition to fuel economy issues, some drivers may find it tedious to repeatedly brake, re-set the target speed, and/or deactivate and reactivate the cruise control system.
Conventional cruise control systems also may result in relatively low fuel economy in areas of variable terrain (e.g., hilly areas). For example, gravity may cause a vehicle climbing a hill to slow down, which may induce the cruise control system to cause the vehicle aggressively to accelerate to the target speed during the climb (e.g., through downshifting and increased throttle input). After the vehicle reaches the crest of the hill and begins its descent, gravity may cause the vehicle's speed to increase beyond the target speed, which may induce the cruise control system to cause the vehicle to decelerate (e.g., through engine braking). Both the aggressive acceleration maneuver in the climb and the deceleration maneuver in the descent are inherently less fuel efficient than operating on flat terrain. When performed repeatedly (e.g., in areas where hills are numerous), significantly decreased fuel economy may result.
What are needed are cruise control systems and methods of their operation that may result in better fuel economy when compared with the fuel economies achieved using conventional cruise control systems. More particularly, what are needed are cruise control systems and methods that may result in improved fuel economy in areas of heavy traffic, variable speed limits, non-gradual turns, and/or uneven terrain. Other desirable features and characteristics will become apparent from the subsequent detailed description and the appended claims, taken in conjunction with the accompanying drawings and the foregoing technical field and background.